In known motor vehicles with central fuel injection, the aspirated air passes radially from the air filter through a hose into the air inlet chamber. From there it flows axially into the mixture former. Because of this deflection in the air inlet chamber and also simply because the aspirated air is deflected several times before reaching the air inlet chamber, a flow profile results that is not homogeneous in terms of velocity and direction. This leads to distortions of the injection cone of the central fuel injection system. The result is that above a certain flow velocity or engine speed, a drop in output occurs because of poor mixture distribution. Even minor twisting of the hose leading from the air filter to the air inlet chamber causes considerable changes in the maximum possible power output of the internal combustion engine.
To make the flow profile uniform, it is a generally known process to place air conducting surfaces in a flow channel. U.S. Pat. No. 3,814,391, for example, discloses a mixture former which has numerous air conducting surfaces in the intake pipe behind a throttle valve to ensure uniform flow. Placement of deflection surfaces inside a mixture aspiration tube is also known, as disclosed by, for example German Auslegeschrift 1,962,113.